body{
    margin: 0;
    padding:0;
    background: #2d3436;

}
.navigation{
    position: absolute;
    top:50%;
    left:50%;
    transform: translate(-50%,-50%);
}
.btn {
    position: relative;
    display:block;
    color:white;
    font-size:14px;
    font-family: "montserrat";
    text-decoration:none;
    margin: 30px 0;
    border:2px solid #ff7675;
    padding: 14px 50px;
    /*  改变为大写*/
    text-transform: uppercase;
    overflow: hidden;
    /* 缓慢过度1s */
    transition: 1s all ease;

}
.btn::before{
    background: #ff7675;
    content: "";
    /* width: 100%; */
    /* height: 100%; */
    position: absolute;
    top:50%;
    left:50%;
    transform:translate(-50%,-50%);
    z-index: -1;
    transition: all 0.6s ease;

}
.btn1::before{
    width: 0;
    height: 100%;
}
.btn1:hover::before{
    width: 100%;
}
.btn2::before{
    width: 100%;
    height: 0;
}
.btn2:hover::before{
    height: 100%;
}
.btn3::before{
    width: 100%;
    height: 0;
    transform: translate(-50%,-50%) rotate(45deg);
}
.btn3:hover::before{
    height: 400%;
}
.btn4::before{
    width: 100%;
    height: 0;
    transform: translate(-50%,-50%) rotate(-45deg);
}
.btn4:hover::before{
    height: 400%;
}

